The Master Thesis of Arnab De, Indiana University, August 2007 entitled “Design of peptide-based prodrug chemistry and its application to glucagon-like peptide 1” discloses, i.a., the synthesis of GLP-1 ester prodrugs, based on a GLP-1 peptide with a hydroxy-terminal extension instead of an N-terminal amine (see e.g. section D-IV and D-V, class 3 and 4 compounds).
Peptide Science 2010, 94(4), 448-456 (Arnab De et al) relates to synthesis and characterization of ester-based prodrugs of glucagon-like peptide 1.
US 2011/0065633 A1 discloses, i.a., ester-based prodrugs of GLP-1 (see, e.g., Example 4).
Bioorganic & Medicinal Chemistry Letters 2005, (15), 1595-1598 (Santos et al) relates to cyclization-activated prodrugs, more in particular to synthesis, reactivity and toxicity of dipeptide esters of paracetamol. Table 1 shows the rate constants for the release of paracetamol from a dipeptide ester prodrug thereof at pH 7.4 and 37° C. A footnote to compound 4k where Y is methyl explains that the reaction was too fast to be monitoredat 37° C.
Regulatory Peptides 2000, (86), 103-111 (Gallwitz et al) relates to GLP-1-analogues resistant to degradation by dipeptidyl-peptidase IV in vitro.
Annual Review of Pharmacology and Toxicology 1993, (32), 521-544 (Oliyai and Stella) is a review article relating to prodrugs of peptides and proteins for improved formulation and delivery.